U.S. patent number 7,442,196 [Application Number 10/773,608] was granted by the patent office on 2008-10-28 for dynamic knee balancer.
This patent grant is currently assigned to Synvasive Technology, Inc.. Invention is credited to Kevin Cordes, Michael G. Fisher, Anthony K. Hedley, Michael Howard, Toshinobu Katsuya.
United States Patent |
7,442,196 |
Fisher , et al. |
October 28, 2008 |
Dynamic knee balancer
Abstract
Dynamic knee balancing devices, systems and methods provide for
enhanced total knee arthroplasty ("TKA") procedures. Devices
generally include a stationary femoral member for removably
attaching to a distal femur and an adjustable femoral member
coupled with the stationary member for adjusting ligament tension
of the knee. The adjustable femoral member includes at least one
positioning feature for providing positional and/or orientation
information for facilitating the TKA procedure. Additionally, the
adjustable femoral member is movably couplable with a tibial member
engaged with the proximal tibia to allow movement of the knee
through a range of motion without removing the device from the
joint space. When the adjustable femoral member is adjusted, the
positional feature(s) move relative to the distal femur to provide
positional information.
Inventors: |
Fisher; Michael G. (Folsom,
CA), Hedley; Anthony K. (Paradise Valley, AZ), Howard;
Michael (Scottsdale, AZ), Cordes; Kevin (Placerville,
CA), Katsuya; Toshinobu (Kobe, JP) |
Assignee: |
Synvasive Technology, Inc. (El
Dorado Hills, CA)
|
Family
ID: |
37872305 |
Appl.
No.: |
10/773,608 |
Filed: |
February 6, 2004 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20050177169 A1 |
Aug 11, 2005 |
|
Current U.S.
Class: |
606/88; 606/96;
606/120 |
Current CPC
Class: |
A61B
17/02 (20130101); A61F 2/4657 (20130101); A61F
2/4684 (20130101); A61B 17/025 (20130101); A61B
2090/064 (20160201); A61B 17/155 (20130101); A61B
2017/0268 (20130101); A61F 2/38 (20130101); A61F
2002/30092 (20130101); A61F 2002/30428 (20130101); A61F
2002/30507 (20130101); A61F 2002/30538 (20130101); A61F
2002/30553 (20130101); A61F 2002/30566 (20130101); A61F
2210/0014 (20130101); A61F 2220/0025 (20130101); A61F
2250/0006 (20130101); A61F 2250/0008 (20130101) |
Current International
Class: |
A61B
17/17 (20060101); A61B 17/58 (20060101); A61B
17/90 (20060101) |
Field of
Search: |
;606/86-88
;623/20.14-20.36 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Delio, "Hoping for a Knee-Jerk Reaction" Wired News.
2004.,[retrieved on Aug. 22, 2005]. Retrieved from the Internet on
<URL:
http://wiredvig.wired.com/news/medtech/0,1286,62716,00.html?tw=newsletter-
.sub.--to>. cited by other .
Eckhoff et al., "Three-Dimensional Morphology and Kinematics of the
Distal Part of the Femur Viewed in Virtual Reality", Jnl. Bone
& Jt. Surg., vol. 85-A Supplement 4, 2003, 97-104. cited by
other .
Howe et al., "Robotics for Surgery," Annu. Rev. Biomed. Eng. 1999,
01:211-240. cited by other .
Mihalko et al., "Comparison of Ligament-Balancing Techniques During
Total Knee Arthroplasty," Jnl. Bone & Jt. Surg., vol. 85-A
Supplement 4, 2003, 132-135. cited by other .
Palmer et al., "Total Knee Arthoplasty"[online],[retrieved on Dec.
11, 2003]. Retrieved on from the Internet <URL:
http://www.emedicine.com/orthoped/topic347.htm.> (18 pages
total). cited by other .
Rapp, "Electronic Knee Implant May Benefit Future TKR Patients"
Orthopedics Today, vol. 25, No. 3; (Mar. 2005), p. 14-15. cited by
other .
Ries et al., "Soft-Tissue Balance in Revision Total Knee
Arthroplasty," Jnl. Bone & Jt. Surg., vol. 85-A Supplement 4,
2003, 38-42. cited by other .
Ries et al., "Soft-Tissue Balance in Revision Total Knee
Arthroplasty," Jnl. Bone & Jt. Surg., vol. 86-A Supplement 1,
2003, 82-86. cited by other .
The Gray Sheet, "Knee Implant Surgery Techniques Can Obscure Tech
Advances--NIH Panel", FDC Reports "The Gray Sheet", Dec. 15, 2003,
p. 11. cited by other .
The Gray Sheet, "Knee Implant Wear Debris, Changing Demographics
Weighed by NIH Panel", FDC Reports "The Gray Sheet", Dec. 1, 2003,
p. 10. cited by other .
The Gray Sheet, "NIH Consensus: More Knee Replacements Among Young,
Old to Grow Market", FDC Reports "The Gray Sheet", Dec. 15, 2003,
p. 12. cited by other.
|
Primary Examiner: Robert; Eduardo C.
Assistant Examiner: Hoffman; Mary
Attorney, Agent or Firm: Townsend & Townsend & Crew
LLP
Claims
What is claimed is:
1. A device for enhancing a surgical procedure on a knee, the
device comprising: a tibial member having a pair of complementary
depressions, said tibial member being engageable with a surface of
the proximal tibia; at least one stationary femoral member for
removably attaching to a distal femur; and at least one adjustable
femoral member having a first surface disposed to contact the
tibial member when the knee is in extension and having a posterior
condylar member including a medial femoral posterior condylar
portion and a lateral femoral posterior condylar portion, said
posterior condylar member being disposed at a substantially right
angle relative to the first surface so that the medial and lateral
femoral posterior condylar portions slidingly contact the
complementary depressions in the tibial member when the knee is in
flexion, said adjustable femoral member being movably engaged with
the stationary femoral member to adjust tension in at least one
ligament of the knee, the adjustable femoral member including an
adjustment member that moves the adjustable femoral member in an
anterior-posterior direction relative to the stationary femoral
member for facilitating completion of the surgical procedure to
enhance range of motion, stability or patella tracking of the knee;
wherein the adjustable femoral member is movably engageable with
said tibial member engaged with a proximal tibia to allow the knee
to be moved through a range of motion from a fixed position to an
extended position without removing the femoral and tibial
members.
2. A device as in claim 1, wherein the at least one stationary
femoral member is engageable with a surface at the distal end of
the distal femur.
3. A device as in claim 1, wherein the adjustable femoral member is
separately adjustable on a medial side and a lateral side of the
femoral member to adjust tension in the at least one ligament.
4. A device as in claim 3, wherein adjusting on one side relative
to the other side causes the adjustable femoral member to rotate
relative to the distal femur.
5. A device as in claim 4, wherein the adjustment member comprises:
at least one lateral adjustment member for adjusting a lateral
portion of the adjustable member; and at least one medial
adjustment member for adjusting a medial portion of the adjustable
member.
6. A device as in claim 5, wherein the lateral and medial
adjustment members are selected from the group consisting of
screws, pins, levers, rods, springs, spring-loaded mechanisms and
shape memory materials.
7. A device as in claim 1, wherein the at least one adjustable
femoral member further has at least one distal femoral portion for
emulating a distal surface of the femur.
8. A device as in claim 7, wherein the distal femoral portion, the,
medial femoral posterior condylar portion, and the lateral femoral
posterior condylar portion all comprise one piece or extrusion.
9. A device as in claim 7, wherein the at least one stationary
femoral member comprises: at least one distal femoral plate for
coupling the distal femoral portion of the adjustable femoral
member to the distal femur; and wherein the posterior condylar
member extends from the distal femoral portion to contact at least
part of a medial posterior femoral condyle and a lateral posterior
femoral condyle of the distal femur.
10. A device as in claim 9, wherein the distal femoral plate, the
medial femoral posterior condylar member, and the lateral femoral
posterior condylar member all comprise one piece or extrusion.
11. A device as in claim 9, wherein the medial femoral posterior
condylar portion of the adjustable femoral member is adjustable
relative to the medial femoral posterior condylar member of the
stationary femoral member, and wherein the lateral femoral
posterior condylar portion of the adjustable femoral member is
separately adjustable relative to the lateral femoral posterior
condylar member of the stationary femoral member.
12. A device as in claim 1, wherein the adjustable femoral member
is adjustable relative to the stationary femoral member to
separately adjust tension in at least one of a medial collateral
ligament and a lateral collateral ligament of the knee.
13. A device as in claim 1, wherein the at least one adjustable
femoral member comprises at least one self-adjusting member.
14. A device as in claim 13, wherein the at least one
self-adjusting member comprises at least one of a spring-loaded
member and a shape memory member.
15. A device as in claim 13, wherein the at least one
self-adjusting member adjusts relative to the stationary femoral
member to adjust tension in at least one of a medial collateral
ligament and a lateral collateral ligament of the knee.
16. A device as in claim 1, wherein the at least one adjustable
femoral member comprises a plurality of pre-adjusted femoral
members, each having a different asymmetry relative to the
stationary member; wherein one of the pre-adjusted members is
selected for facilitating the surgical procedure to provide a
desired range of motion when the surgical procedure is
completed.
17. A device as in claim 1, wherein the adjustment member of the
adjustable femoral member is selected from the group consisting of
an aperture, a drill bit guide, a surface marker, a surface
feature, a measurement device, an embedded marker, a fiducial, a
transponder, a transceiver and a sensor.
18. A device as in claim 17, wherein the adjustment member
facilitates at least one of placing a cutting guide on the distal
femur for making bone cuts, making one or more bone cuts on the
distal femur, and positioning a prosthetic femoral component on the
distal femur.
19. A device as in claim 17, wherein the adjustment member
comprises at least two apertures.
20. A device as in claim 19, wherein each of the at least two
apertures is configured to guide a drill bit to form a hole in the
distal femur for attaching a cutting guide to the femur.
21. A device as in claim 19, wherein each of the at least two
apertures are configured to receive at least one of a marker, a
fiducial, a transponder, a transceiver and a sensor.
22. A device as in claim 19, wherein the at least two apertures
extend through the adjustable femoral member and through apertures
in the stationary femoral member to provide access to the distal
femur.
23. A device as in claim 22, wherein the at least two apertures are
positioned slightly asymmetrically on the adjustable femoral member
to provide for a built-in desired flexibility in the ligaments when
the surgical procedure is completed.
24. A device as in claim 17, wherein at least one of the adjustable
femoral member and the adjustment member is asymmetrically oriented
relative to the stationary member to provide built-in enhanced
range of motion when the surgical procedure is completed.
25. A device as in claim 24, further comprising multiple adjustable
femoral members, each having a different asymmetry relative to the
stationary member, wherein one of the multiple adjustable femoral
members is selected for facilitating the surgical procedure to
provide a desired range of motion when the surgical procedure is
completed.
26. A device as in claim 1, wherein the tibial member comprises at
least one shim, paddle, plate, bar, platform or rod.
27. A device as in claim 26, wherein the tibial member comprises a
plurality of tibial shims having different thicknesses or heights,
wherein any one of the plurality of shims may be selected for
engaging with the surface of the proximal tibia to provide a
desired amount of tension in the ligaments.
28. A device as in claim 27, wherein the tibial member further
comprises a plate for removably attaching to the surface of the
proximal tibia, disposed between the surface and the selected
tibial shim.
29. A device, as in claim 1, wherein the femoral member and the
tibial member are configured to be movably coupled via force
provided by the at least one ligament of or adjacent the knee.
30. A device as in claim 1, wherein the femoral and tibial members,
when engaged with the distal femur and proximal tibia respectively,
are disposed primarily within a joint space between the distal
femur and the proximal tibia.
31. A device as in claim 30, wherein a patella of the knee remains
approximately in its anatomical position while the femoral and
tibial members are engaged and the knee is moved through the range
of motion.
32. A device as in claim 1, wherein the movable coupling of the
femoral and tibial members allows for flexion and extension through
the range of motion.
33. A device as in claim 32, wherein the range of motion comprises
a range from approximately full extension of the knee to
approximately full flexion of the knee.
34. A device as in claim 1, wherein the stationary femoral member
comprises at least one material selected from the group consisting
of plastics, composites, aluminum, stainless steel, composite,
cobalt-chrome, titanium, and other metals.
35. A device as in claim 1, wherein the adjustable femoral member
comprises at least one material selected from the group consisting
of plastics, composites, aluminum, stainless steel, composite,
cobalt-chrome, titanium, and other metals.
36. A device as in claim 1, further comprising at least one
grasping member coupled with at least one of the stationary and
adjustable femoral members for facilitating placement and/or
removal of the device from the knee.
37. A device as in claim 1, wherein the adjustable femoral member
is configured to be adjusted to identify at least one position on
the distal femur for rotationally orienting a guiding device on the
femur to make at least one bone cut for positioning of an implanted
prosthetic femoral device, the position of the implanted device
enhancing at least one of range of motion, stability and patella
tracking of the knee.
38. A device as in claim 37, wherein the guiding devices is a
cutting guide, a fiducial, a marker, a transponder or a transceiver
and sensor.
39. A device as in claim 1, wherein the at least one stationary
femoral member comprises: at least one distal femoral plate for
removably attaching to the distal femur; and at least one
stationary posterior condylar member extending substantially
perpendicular from the distal femoral plate to contact at least
part of a medial posterior femoral condyle or a lateral posterior
femoral condyle of the distal femur.
40. A device as in claim 1, wherein the adjustable femoral member
comprises a plate and the posterior condylar member extends
substantially perpendicularly from the plate.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to medical/surgical
devices, systems and methods. More specifically, the invention
relates to devices, systems and methods for enhancing a knee
surgery procedure.
Total knee replacement surgery, also referred to as total knee
arthroplasty ("TKA"), is becoming an increasingly important
treatment for chronic knee pain and joint dysfunction. A recent
panel of the National Institutes of Health at a Consensus
Development Conference recognized that approximately 300,000 TKA
surgeries are performed annually in the U.S. for end-stage knee
arthritis. The NTH panel agreed that although advances have been
made in TKA surgical devices and techniques, improved outcomes
through further innovations should still be diligently pursued. The
panel concluded that techniques for placing artificial knee
prostheses, in particular, should be improved to provide better
outcomes and reduce wear of the prostheses, to thus reduce the need
for repeat TKA surgeries. If advances in TKA continue to be made,
the procedure may become more readily available to younger
patients, obese patients, and the like, who may need TKA but who do
not fall within in the "ideal" age range traditionally defined as
between 60 and 75 years old. Improved techniques and devices would
also mean enhanced outcomes for all TKA patients, with better
functioning of the knee joint and longer useful life of the
prosthetic knee.
The knee is generally defined as the point of articulation of the
femur with the tibia. Structures that make up the knee include the
distal femur, the proximal tibia, the patella, and the soft tissues
within and surrounding the knee joint. Four ligaments are
especially important in the functioning of the knee--the anterior
cruciate ligament, the posterior cruciate ligament, the medial
collateral ligament, and the lateral collateral ligament. In an
arthritic knee, protective cartilage at the point of articulation
of the femur with the tibia has been worn away to allow the femur
to directly contact the tibia. This bone-on-bone contact causes
significant pain and discomfort. The primary goals of a TKA
procedure are to replace the distal end of the femur, the proximal
end of the tibia, and often the inner surface of the patella with
prosthetic parts to avoid bone-on-bone contact and provide smooth,
well-aligned surfaces for joint movement, while also creating a
stable knee joint that moves through a wide range of motion.
One of the greatest challenges in TKA surgery is to properly
balance ligament tension, especially in the medial and lateral
collateral ligaments, through a full range of motion of the knee.
The collateral ligaments, which connect the distal femur and
proximal tibia on the medial and lateral aspects of the knee,
account for much of the stability and movement of the knee. If one
of the collateral ligaments is too lax or too tight relative to the
other collateral ligament, the knee will typically be unstable,
range of motion may be limited, the patella may track improperly,
and the femur and/or tibia may wear unevenly, leading to arthritis
and pain. Uneven ligament tension after TKA surgery will typically
cause joint instability and poor patellar tracking, limited range
of motion, and impaired function of the knee, as well as uneven,
increased wear of the prosthetic device, which often necessitates
repeat surgery. Thus, it is imperative for the short- and long-term
success of a TKA procedure to achieve balanced ligament tension in
the knee through a full range of motion.
Balancing ligament tension during TKA surgery is complicated by the
fact that the natural knee does not operate like a hinge moving
about a single axis. The knee exhibits dynamic external rotation of
the tibia relative to the femur as the knee moves from its flexed
to its fully extended position. This automatic rotation of the
tibia occurs in the opposite direction when the knee is flexed from
its fully extended position to produce an internal rotation of the
tibia relative to the femur. Thus, the natural knee exhibits a
rotary laxity that allows the tibia to rotate through a limited
internal and external arc, during knee flexion. Additionally, the
femur translates anteriorly and posteriorly as the tibia is being
flexed about it, bringing yet another movement variable into the
equation. Thus, the ligaments of the knee, along with the femur,
tibia and patella, create a truly dynamic bio-mechanism, making
ligament tension balancing in TKA surgery extremely challenging.
Many articles and studies have been devoted to ligament tension
balancing in TKA, such as the following: Mihalko, WH et al.,
"Comparison of Ligament-Balancing Techniques During Total Knee
Arthroplasty," Jnl. Bone & Jt. Surg., Vol. 85-A Supplement 4,
2003, 132-135; Eckhoff, D G et al., "Three-Dimensional Morphology
and Kinematics of the Distal Part of the Femur Viewed in Virtual
Reality, Jnl. Bone & Jt. Surg., Vol. 85-A Supplement 4, 2003,
97-104; and Ries, M D, et al., "Soft-Tissue Balance in Revision
Total Knee Arthroplasty," Jnl. Bone & Jt. Surg., Vol. 85-A
Supplement 4, 2003, 38-42.
One technique for balancing collateral ligament tension during a
TKA procedure involves cutting fibers of one or both ligaments to
decrease ligament tension--a technique referred to as "ligament
release." Although ligament release is still commonly used, the
disadvantage of this technique is that it requires actually cutting
ligament tissue, thus weakening the ligament(s) and leaving less
room for error if future releases or TKA procedures are
required.
Rather than or in addition to ligament release, the components of a
total knee prosthesis may be selected and positioned to balance
ligament tension. Since the femoral and tibial components of the
prosthesis are attached to cut surfaces of the distal femur and
proximal tibia respectively, placement and orientation of the bone
cuts are also critically important. Typically, the tibial component
of the prosthesis is positioned on a flat, horizontal cut surface
of the proximal tibia (at a 90 degree angle relative to the long
axis of the tibia), and the position and orientation of the tibial
component typically do not vary greatly from knee to knee.
Therefore, most of the variation in positioning of the total knee
prosthesis typically occurs in positioning the femoral component
and the femoral bone cuts. The surgeon attempts to make these
femoral bone cuts to achieve a position and orientation of the
femoral prosthetic component so as to optimally balance ligament
tension through a full range of motion of the knee. As with
ligament release however, it is often very challenging to position
the femoral bone cuts and femoral prosthetic component to provide
ideal ligament tension through the range of motion. This is due
primarily to the complexity of motion about the knee, as described
above, and the difficulty of placing the femoral component so as to
maintain desired ligament tension through the full range of motion.
Specifically, the rotational, proximal/distal and
anterior/posterior orientations and locations of the femoral
component are all critical for duplicating the kinematics of the
knee.
In a typical TKA procedure, multiple cuts are made to the distal
femur before attaching the femoral component of the prosthesis.
Most procedures, for example, involve making a distal cut across
the distal end of the femur, anterior and posterior cuts, and
angled anterior and posterior chamfer cuts to help secure the
femoral component solidly in place. In order to effectively and
accurately make these resections, orthopedic surgeons typically use
a cutting block or cutting guide, used to guide a surgical saw
blade or rotary tool, which is temporarily attached to the distal
end of the femur. Positioning of such a cutting block, therefore,
is crucial to forming well-positioned bone cuts for attachment of
the femoral prosthetic component.
A number of devices and techniques have been described that attempt
to facilitate ligament balancing during a TKA procedure. Some
techniques, such as those described in U.S. Pat. No. 5,733,292,
involve trial prosthesis components which are used after femoral
and tibial bone cuts are made to assess ligament tension. Some
devices, such as those described in U.S. patent application
Publication No. 2003/0187452, are used to measure a gap between the
distal femur and proximal tibia in extension and to help a surgeon
recreate that same gap when the knee is in flexion. Other "gap
checking" devices are described in U.S. Pat. No. 6,575,980. Other
devices have been developed to help measure an amount of ligament
tension or to apply a desired amount of tension to the ligaments.
U.S. Pat. No. 4,501,266, for example, describes a knee distraction
device for applying a desired amount of tension. Many paddle-like
devices have been suggested for applying or measuring tension
across a knee joint, such as the devices described in U.S. Pat.
Nos. 5,597,379; 5,540,696; 5,800,438; 5,860,980; 5,911,723; and
6,022,377.
One proposed alternative to the cutting block technique for making
bone cuts on a distal femur involves the use of robotic surgical
systems for making distal femoral bone cuts. With robotic surgery
and surgical navigation, a surgical saw blade or bur is still used,
but the bone cuts are positioned as a result of fiducial-based or
shape-based registration of the patient's anatomy. In
fiducial-based approaches, fiducials, or markers are attached to
pertinent anatomical structures prior to imaging. During surgery,
the markers are exposed, and a sensor system conveys their location
to the computer. A wide variety of sensing systems available,
including optical trackers, electromagnetic transceivers,
articulated probe arms, and ultrasonic and laser range finders. In
shape-based approaches, the shapes of anatomical structures are
fitted to preoperative image data. The patient measurements can be
obtained from a variety of sensing techniques, including tracing
curves, scanning distances, or processing images, via one or some
of the aforementioned sensing systems. One description of the use
of robotic surgery systems in knee surgery procedures is found in
Howe, R D, and Matsuoka, Y, "Robotics for Surgery," Annu. Rev.
Biomed. Eng. 1999, 01:211-240.
Although some of the devices and techniques described above have
helped enhance and facilitate TKA procedures, currently available
devices and techniques still have a number of shortcomings. Most
importantly, currently available devices do not allow a physician
to adjust ligament tension in a knee and also receive positional
information based on that adjustment that can be used to facilitate
completion of the TKA surgery. For example, many currently
available devices are applied only in extension or only in flexion
of the knee, or must be removed and replaced when the knee is moved
from extension to flexion. Thus, it is difficult or impossible to
assess ligament tension through the full range of motion using many
currently available devices. Some devices rely on measuring a gap
or amount of tension in extension and then recreating the gap or
tension in flexion. Again, this does not always result in
collateral ligament balance throughout the range of motion. Still
other devices are very cumbersome and/or complex. Many include
large parts which fit external to the knee joint and necessitate
the patella being moved to the side during measurement or other
phases of the TKA procedure. Furthermore, current devices typically
do not reside primarily within the joint space during a surgical
procedure to allow for the natural movements, rotations and
translations of the tibia and femur as the knee is flexed through a
range of motion. In some techniques, bone cuts are made before
ligament balancing is achieved, thus often requiring re-cutting of
those same bone cuts. More bone cuts mean more trauma to the
patient, a longer recovery period, and less bone to work with if a
second TKA is required later in life.
Although robotic surgery may provide a level of improvement over
more traditional techniques, it is typically difficult or
impossible using current robotic techniques to dynamically mark or
register and sense the proper dynamic position to make
well-positioned, subsequent bone cuts for attachment of the femoral
prosthetic component. Thus, even with robotic systems, it is still
challenging to achieve a desired ligament balance to enhance knee
stability, range of motion and patellar tracking. These and other
shortcomings of currently available devices and methods continue to
make ligament balancing, and specifically collateral ligament
balancing, one of the most challenging aspects of TKA surgery.
Therefore, a need exists for improved devices, systems and methods
for enhancing TKA surgery and specifically for dynamically
balancing ligaments during TKA to improve range of motion,
stability, and patellar tracking of the prosthetic knee joint.
Ideally, such devices would help a surgeon balance ligaments
dynamically, through a full range of motion of the knee, allowing
for the natural rotation of the tibia and the natural translation
of the femur while the tibia is being flexed about it. Also
ideally, such devices and methods would allow a surgeon to achieve
a desired ligament tension balance before committing to and making
final bone cuts to the femur. Such devices would also ideally be
simple to use in conjunction with cutting guides, saw blades or
burs, and robotic and navigational systems, preferably allowing the
patella to remain in place during assessment of ligament tension.
At least some of these objectives will be met by the present
invention.
BRIEF SUMMARY OF THE INVENTION
The present invention provides devices, systems and methods for
enhancing knee surgery procedures, and more specifically total knee
replacement procedures (total knee arthroplasty, "TKA"). Various
embodiments generally include a stationary femoral member for
removably attaching to a distal femur and an adjustable femoral
member coupled with the stationary member for providing
adjustability. The adjustable member is movably couplable with a
tibial member engaged with the proximal tibia of the knee, allowing
for the natural movements, rotations and translations of the tibia
and femur to take place as the knee is flexed and/or extended
through a range of motion, resulting in dynamic ligament tension
balancing through a range of motion of the knee.
The adjustable femoral member is adjustable to adjust tension in at
least one ligament of or adjacent the knee. Typically, the
adjustable member is separately adjustable on either side to adjust
tension in the lateral and/or medial collateral ligaments adjacent
the knee. When the adjustable femoral member is adjusted to adjust
ligament tension, one or more positioning features of the
adjustable member provide positioning information to help position
and/or orient a cutting guide, surgical saw blade, bur, mill,
surgical navigation system, robotic surgical system or the like.
This positioning information is then typically used to make
subsequent bone cuts to the distal femur, or to otherwise mill or
shape the distal femur, so that when a femoral prosthetic component
is applied, the knee has a desired stability, range of motion
and/or patellar tracking. Devices and methods of the invention thus
help to dynamically balance ligament tension in a knee during TKA
surgery, without requiring ligament releases, to provide for a
dynamically balanced knee after the surgery is complete.
For purposes of the present description, the terms "ligaments of
the knee," "ligaments in the knee," "ligaments adjacent the knee,"
and the like are all synonymous and all refer generally to any
ligaments within the knee joint space, around the knee, adjacent
the knee, or near the knee. These terms typically refer to the
ligaments that assist in the functioning of the knee, and often the
ligaments referred to are the medial collateral ligament, the
lateral collateral ligament, the anterior cruciate ligament and the
posterior cruciate ligament. Although the following description
focuses on the use of various embodiments in TKA surgical
procedures, these and/or other embodiments may suitably be used to
facilitate other knee surgery procedures, other orthopedic joint
surgery procedures and the like.
That being said, in one aspect of the present invention, a device
for enhancing a surgical procedure on a knee includes at least one
stationary femoral member for removably attaching to a distal femur
and at least one adjustable femoral member movably coupled with the
stationary member to adjust tension in at least one ligament of or
adjacent the knee. The adjustable femoral member includes at least
one positioning feature that moves relative to the distal femur as
the adjustable femoral member is adjusted and thus identifies at
least one position on the distal femur for facilitating completion
of the surgical procedure to enhance at least one of range of
motion, stability and patella tracking of the knee. Furthermore,
the adjustable femoral member is movably couplable with at least
one tibial member engaged with a proximal tibia to allow the knee
to be moved through a range of motion without removing the femoral
and tibial members.
In some embodiments the stationary femoral member is engageable
with a cut surface at the distal end of the distal femur.
Similarly, in some embodiments the tibial member is engageable with
a cut surface at the proximal end of the tibia. Typically, the
adjustable femoral member is separately adjustable on a medial side
and a lateral side of the femoral member to adjust tension in the
at least one ligament. In some embodiments, adjusting on one side
relative to the other side causes the adjustable femoral member to
rotate relative to the anterior and posterior aspects of the distal
femur.
Adjustment of the at least one adjustable member may be
accomplished via any suitable adjustment device, components,
techniques and the like. For example, in some embodiments the
adjustable member includes at least one lateral adjustment member
for adjusting a lateral portion of the adjustable member and at
least one medial adjustment member for adjusting a medial portion
of the adjustable member. The adjustment members may comprise
screws, pins, levers, spring-loaded members or any other suitable
device or devices for conferring adjustability. In other
embodiments, the adjustable femoral member may be partially or
completely self-adjusting, for example via one or more
spring-loaded or shape memory self-adjusting members or the like.
In still other embodiments, the at least one adjustable femoral
member comprises multiple pre-adjusted femoral members, each
pre-adjusted femoral member conferring different amounts of
ligament tensioning and balancing about the knee. A surgeon may
choose any one of the pre-adjusted femoral members for balancing
ligament tension, and may try more than one pre-adjusted member
before deciding which to use. Thus, by the terms "adjustable,"
"adjustable femoral member," "adjustability" and the like it is
meant that one or more members may be used to adjust ligament
tension in the knee. In various embodiments, adjustability may be
achieved via one or more adjustable members, self-adjusting
members, interchangeable pre-adjusted members, or any other
suitable devices.
In various embodiments, a device for enhancing knee surgery may be
used interchangeably for either a left knee or a right knee. In
other words, some embodiments of a knee surgery device are not
typically specific to either a left knee or a right knee, although
such left-side-specific/right-side-specific devices are
contemplated. Thus, because the typical knee balancing device of
the present invention is used on either knee, the terms "medial"
and "lateral" should not be interpreted as limiting a device to use
for either a left knee or a right knee. For example, an adjustment
member that is oriented laterally relative to a right knee will be
oriented medially relative to a left knee.
In some embodiments, the at least one adjustable femoral member
comprises at least one distal femoral portion for emulating the
distal condylar surface of the femur and at least one posterior
condylar portion to emulate posterior condylar surfaces of the
femur. In some embodiments, the at least one posterior condylar
portion comprises a medial femoral posterior condylar portion and a
lateral femoral posterior condylar portion. In one embodiment, the
distal femoral portion, the medial femoral posterior condylar
portion and the lateral femoral posterior condylar portion are all
one piece or extrusion. In other embodiments, these portions may be
multiple, coupled parts. The distal and posterior condylar portions
allow the femoral member to movably engage with the tibial member
to allow the knee to be moved through a range of motion while the
device is engaged with the knee.
In some embodiments, the distal femoral portion and posterior
condylar portions of the adjustable femoral member are movably
couplable with one or more complementary depressions in the tibial
member. For example, the posterior condylar members may comprise a
medial femoral posterior condylar member slidably couplable with a
medial depression of the tibial member and a lateral femoral
posterior condylar member slidably couplable with a lateral
depression of the tibial member.
In some embodiments, the at least one stationary femoral member
comprises at least one distal femoral plate for coupling the distal
femoral portion of the adjustable femoral member to the distal
femur and at least one posterior condylar member wrapping around
from the distal femoral portion to contact at least part of a
medial posterior femoral condyle and a lateral posterior femoral
condyle of the distal femur. Optionally, the posterior condylar
members comprise a medial femoral posterior condylar member and a
lateral femoral posterior condylar member. Often, in such
embodiments, the medial femoral posterior condylar portion of the
adjustable femoral member is adjustable relative to the medial side
of the stationary femoral member, and the lateral femoral posterior
condylar portion of the adjustable femoral member is separately
adjustable relative to the lateral side of the stationary femoral
member. In some embodiments, the distal femoral portion and
posterior condylar members of the stationary femoral member may
comprise one piece or extrusion. In alternative embodiments, the
stationary femoral member may comprise multiple coupled parts.
The adjustable member may be adjustable in any number of ways, but
in one embodiment it is adjustable relative to the stationary
femoral member to separately adjust tension in the medial
collateral ligament and/or the lateral collateral ligament of the
knee. In making such adjustments, tension of other ligaments, such
as the anterior and/or posterior cruciate ligaments, may also be
adjusted. In some embodiments, the adjustable femoral member
self-adjusts relative to the stationary femoral member to
separately adjust tension in the medial collateral ligament,
lateral collateral ligament and/or other ligaments.
When the adjustable femoral member is adjusted to adjust and
balance ligament tension, the at least one positioning feature
moves relative to the distal femur and the stationary member. The
post-adjustment position of the positioning feature(s) provides
positional information which may then be used for completing the
TKA procedure. For example, such information may be used to
position a cutting guide on the distal femur for making subsequent
bone cuts, to make the bone cuts themselves, to apply the femoral
prosthetic component to the distal femur, and/or the like. The
positioning features themselves may comprise any of a number of
different features, such as but not limited to one or more
apertures, drill bit guides, surface markers, surface features,
measurement devices, embedded markers, fiducials, transponders,
transceivers and/or sensors.
In one embodiment, for example, two or more apertures act as the
positioning features. In some embodiments, these apertures rotate
relative to the distal femur when the adjustable femoral member is
adjusted. Additionally or alternatively, the apertures may move in
an anterior and/or posterior direction relative to the distal
femur. The apertures may provide information in a number of
different ways. For example, they may act as drill bit guides to
guide the drilling of holes into the distal femur for attachment of
a cutting guide. Typically, such apertures extend through the
adjustable member and through apertures in the stationary femoral
member to the distal femur to allow for passage of the drill bit.
Alternatively, fiducials, sensors, transmitters, markers or the
like may be disposed in the apertures and may send or receive
signals or act as markers for use by external devices. In one
embodiment, for example, a robotic surgical system and/or a
navigational system may use the position of such fiducials,
sensors, markers or the like to help guide a surgical saw blade,
bur or the like to shape the distal femur. Optionally, the
apertures may be positioned slightly asymmetrically on the
adjustable member to provide for a built-in desired flexibility in
the ligaments, to achieve enhanced range of motion, stability, and
patellar tracking of the prosthetic knee joint, when the surgical
procedure is completed. In another embodiment, the at least one
adjustable femoral member may be asymmetrically oriented relative
to the stationary member to provide built-in desired flexibility in
the ligaments, to achieve enhanced range of motion, stability, and
patellar tracking of the prosthetic knee joint, when the surgical
procedure is completed.
Any other suitable positioning feature or combination of features
may be included in the adjustable femoral member, including any
feature now known or hereafter discovered. Furthermore, the
positional information derived from such positioning features may
be generated and used in any suitable fashion. For example,
positional features may act as markers which may be queried by an
external system, such as a navigational or robotic system.
Positional information may then be generated and/or processed via a
computer and data regarding post-adjustment positions, pressures,
ligament tensions at various points in a range of motion may be
provided to a user and/or to a robotic surgery device. Positional
information may also be provided by mechanical means such as torque
applied and adjusted to the adjustment mechanism of the adjustable
member. Generally, any suitable positioning feature may be used and
any positional information, ligament tension information and/or the
like may be generated by various embodiments of the invention.
Typically, the at least one tibial member is engageable with a cut
surface of the proximal tibia. Examples of tibial members include
but are not limited to shims, paddles, plates, bars, platforms and
rods. In a preferred embodiment, a plurality of tibial shims are
provided, having different thicknesses or heights, and any one of
the plurality of shims may be selected for engaging with the cut
surface of the proximal tibia to provide a desired amount of
tension in the ligaments. Optionally, the at least one tibial
member may further comprise a plate for removably attaching to the
cut surface of the proximal tibia, disposed between the cut surface
and the selected tibial shim.
In one embodiment, the femoral and tibial members are movably
coupled via force provided by at least one ligament adjacent the
knee. More specifically, in one embodiment the femoral and tibial
members are coupled only via force provided by ligament force. This
coupling of the femoral and tibial members by ligament force may be
described as "dynamic" coupling. Such coupling helps allow ligament
tension to be balanced with a device that resides primarily within
the joint space and also allows for the natural movements,
rotations and translations of the tibia and femur to take place as
the knee is flexed through a range of motion, resulting in dynamic
ligament tension balancing through a range of motion of the knee.
Thus, in one embodiment the femoral and tibial members, when
engaged with the distal femur and proximal tibia respectively, are
disposed primarily within a joint space between the distal femur
and the proximal tibia. In such embodiments, a patella of the knee
may remain approximately in its anatomical position while the
femoral and tibial members are engaged and the knee is moved
through the range of motion during the TKA procedure. The movable
coupling of the femoral and tibial members allows for flexion and
extension through the range of motion. By "range of motion," it is
meant that the knee is moved from extension to flexion and/or from
flexion to extension. In some embodiments, the range of motion
comprises a range from approximately full extension of the knee to
approximately full flexion of the knee. In other embodiments the
range of motion may be narrower.
Components of the femoral and tibial members may be manufactured
from any materials or combinations of materials known in the art or
hereafter discovered. For example, in one embodiment either or both
the stationary femoral member and the adjustable femoral member
comprise at least one material selected from the group consisting
of plastics, composites, aluminum, stainless steel, composite,
cobalt-chrome, titanium, and other metals. In some embodiments, the
femoral and/or tibial members may further include at least one
grasping member for facilitating placement and/or removal.
In another aspect of the present invention, a system for enhancing
a surgical procedure on a knee comprises at least one femoral
member removably engageable with a distal femur and at least one
tibial member removably engageable with a proximal tibia and
movably couplable with the femoral member to allow the knee to be
moved through a range of motion without removing the femoral and
tibial members. The femoral member includes at least one stationary
member for attaching to the distal femur and at least one
adjustable femoral member movably coupled with the stationary
member to adjust tension in at least one ligament of or adjacent
the knee. The adjustable femoral member includes at least one
positioning feature that moves relative to the distal femur as the
adjustable femoral member is adjusted and thus identifies at least
one position on the distal femur for facilitating completion of the
surgical procedure to enhance at least one of range of motion,
stability and patella tracking of the knee. Such a system may
include any of the features described above.
As with the various embodiments of the devices described above,
adjustment of the at least one adjustable member may be
accomplished by any suitable means. Thus, in various embodiments of
the system the at least one adjustable femoral member may include
one or more adjustable members, self-adjusting members,
interchangeable pre-adjusted members, or any other suitable devices
for conferring adjustability.
In still another aspect of the present invention, a method for
facilitating a surgical procedure on a knee involves: engaging at
least one femoral member with a distal femur to movably couple with
a tibial member engaged with a proximal tibia, the femoral member
comprising at least one stationary member and at least one
adjustable member; moving the knee; and adjusting the adjustable
femoral member to apply tension to at least one of the ligaments of
or adjacent the knee, thus moving at least one positioning feature
of the adjustable femoral member relative to the distal femur to
identify at least one position on the distal femur for facilitating
completion of the surgical procedure.
Typically, though not necessarily, the tibial member is engaged
with a cut surface of the proximal tibia, and the femoral member is
engaged with a cut surface of the distal femur. As mentioned above,
in some embodiments the tibial and femoral members are engaged
primarily within a joint space between the cut surfaces of the
proximal tibia and the distal femur and are movably coupled via
force provided by the at least one ligament adjacent the knee. This
coupling of the femoral and tibial members by ligament force may be
described as "dynamic" coupling. Such coupling helps allow ligament
tension to be balanced with a device that resides primarily within
the joint space and also allows for the natural movements,
rotations and translations of the tibia and femur to take place as
the knee is flexed through a range of motion, resulting in dynamic
ligament tension balancing through a range of motion of the
knee.
In some embodiments, engaging the tibial member comprises selecting
the tibial member from a plurality of tibial members with different
dimensions, the selected tibial member having dimensions to apply a
desired amount of tension to the at least one ligament. Engaging
the femoral member, in some embodiments, involves attaching a
stationary portion of the femoral member to the distal surface of
the femur, with an adjustable portion of the femoral member being
coupled with the stationary portion. In some embodiments, moving
the knee comprises sliding at least one distal femoral condylar and
posterior condylar member of the femoral member along at least one
complementary depression in the tibial member. More generally,
moving the knee may involve sliding the tibial member along the
femoral member.
In some embodiments, moving the knee may involve moving from
approximately full extension to approximately full flexion.
Alternatively, moving the knee may involve moving from
approximately full flexion to approximately full extension. In some
embodiments, the knee may be moved between extension and flexion
more than once, either before, after or during adjustment of the
adjustable member. For example, in some embodiments the method may
further involve moving the knee after the adjustment step and
further adjusting the adjustable femoral member. Any combination of
knee movements and adjustments is contemplated within the scope of
the present invention. For example, a method may involve moving the
knee through a range of motion to help determine the desired
ligament tension balance in the knee during the range of motion. In
some embodiments, at least the moving and adjusting steps are
performed with the patella of the knee located approximately its
anatomic position over the knee.
Adjusting the adjustable femoral member, in some embodiments,
involves adjusting tension in at least one of a medial collateral
ligament and a lateral collateral ligament. Sometimes adjusting the
adjustable femoral member comprises enlarging a joint space between
at least part of the distal femur and proximal tibia to apply
tension to at least one of the ligaments. Enlarging the joint space
may involve enlarging the space primarily at a medial side of the
knee or primarily at a lateral side of the knee in various
embodiments. Typically, enlarging the space applies tension to the
medial collateral ligament, the lateral collateral ligament or
both. In some embodiments, adjusting the adjustable femoral member
comprises moving an adjustable portion of the femoral member
relative to a stationary portion of the femoral member. For
example, adjusting the adjustable femoral member may involve
adjusting at least one adjustment member on the adjustable femoral
member. In one embodiment, for example, one or more screws may be
turned to adjust the adjustable femoral member.
In some embodiments, adjusting the adjustable femoral member causes
at least one positioning feature on the femoral member to be
oriented to the distal end of the femur, the positioning feature(s)
helping determine a position for applying a cutting guide to the
distal femur, for orienting a surgical navigation system sensor,
for locating and or making subsequent bone cuts, or the like. In
some embodiments, for example, the at least one positioning feature
comprises one or more apertures for guiding a drill bit for forming
one or more drill holes used to attach a cutting guide, for
dynamically orienting a bone cutting device, for dynamic placement
of fiducials or markers to orient a surgical navigation system
sensor to the distal end of the femur, or the like. In some
embodiments, the least one aperture comprises at least two
apertures, and adjusting the adjustable femoral member causes the
at least two apertures to rotate relative to one another over the
distal end of the femur. For example, the apertures may rotate
about an axis approximately corresponding to a long axis of the
distal femur. Alternatively or additionally, adjusting the
adjustable femoral member may cause the at least one aperture to
move in an anterior or posterior direction relative to the distal
femur. Of course, as described above, any suitable positioning
features may be included on the adjustable member, and any methods
for acquiring or using positional information may be employed in
various embodiments.
In some embodiments, the method further involves: placing at least
one hole or slot in the distal end of the femur, using the at least
one aperture to guide a tool bit; removing the adjustable femoral
member from the distal femur; using the at least one hole for
attaching a cutting guide to the distal end of the femur; and
making at least one cut on the distal end of the femur. Optionally,
such a method may further include attaching a femoral prosthesis
component to the cut distal end of the femur and attaching a tibial
prosthesis component to a cut surface of the proximal tibia. In
alternative embodiments, the method may further include sending one
or more signals from the at least one positioning device to a
distal femur cutting device and cutting the distal femur with the
cutting device, based on the signal(s). Such signals, for example,
may be used as part of a navigational system and/or robotic
surgical system.
Further details of these and other embodiments are described more
fully below, with reference to the attached drawing figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a frontal view of a knee in extension, with a knee
balancing device according to one embodiment of the invention in
place within the knee joint;
FIG. 1B is a side view of the knee in extension and knee balancing
device shown in FIG. 1A;
FIG. 1C is a side view of the knee and knee balancing device shown
in FIGS. 1A and 1B, with the knee in a position of flexion;
FIG. 1D is a side view of the knee and knee balancing device shown
in FIGS. 1A-1C, with the knee balancing device adjusted to achieve
a desired ligament tension balance according to one embodiment of
the invention;
FIG. 1E is a frontal view of the knee and knee balancing device
shown in FIGS. 1A-1D, with the knee balancing device adjusted to
achieve a desired ligament tension balance according to one
embodiment of the invention;
FIG. 2A is a frontal view of a knee balancing device according to
one embodiment of the present invention;
FIG. 2B is a rear view of the knee balancing device shown in FIG.
2A;
FIG. 2C is a side view of the knee balancing device shown in FIGS.
2A and 2B;
FIG. 3A is a front-perspective view of a knee balancing device
according to one embodiment of the present invention;
FIG. 3B is a rear-perspective view of the knee balancing device
shown in FIG. 2A;
FIG. 3C is a front-perspective view a knee balancing device
according to another embodiment of the present invention
FIG. 4A is a front-perspective, exploded view of a knee balancing
device according to one embodiment of the present invention;
and
FIG. 4B is a rear-perspective, exploded view of the knee balancing
device shown in FIG. 4A.
DETAILED DESCRIPTION OF THE INVENTION
As discussed above, the present invention provides devices, systems
and methods primarily intended for enhancing total knee
arthroplasty (TKA) surgical procedures. Although these devices,
systems and methods are used primarily in TKA, however, some
embodiments may be used to enhance other knee surgery procedures or
surgical procedures on other joints, such as an elbow joint.
That being said, devices, systems and methods of the invention
generally help a surgeon to balance ligament tension in a knee
during a TKA procedure and thereby help the surgeon perform the TKA
so as to achieve a desired ligament balance when the surgery is
complete. Devices, systems and methods of the invention generally
facilitate dynamic balancing of ligaments of the knee, such that
these ligaments remain balanced through a range of motion about the
knee. Oftentimes, such dynamic balancing helps create a prosthetic
knee that has a desirable level of stability, patellar tracking and
range of motion.
With reference now to FIG. 1A, a frontal view of a right knee K is
shown in extension, with a knee balancing system 10 in place within
the knee joint space. The anatomical components of the knee K that
are pertinent to this description include a distal femur F, a
proximal tibia T, a medial collateral ligament MCL, and a lateral
collateral ligament LCL. (Also labeled is the proximal fibula Fi,
to which the LCL attaches.) The knee K is shown without a patella,
medial collateral ligament or lateral collateral ligament, for
clarity, but many embodiments may be used while the patella is in
its anatomical position on the anterior aspect of the knee K. In
FIG. 1A, a portion of the distal end of the distal femur F and a
portion of the proximal end of the proximal tibia T have been cut
or shaved off, to create level surfaces on which to place femoral
member 12 and a tibial member 14, respectively, of dynamic knee
balancing system 10. In various embodiments, a knee balancing
device may be provided as only a femoral member, for example to be
used with off-the-shelf tibial trial inserts. In other embodiments,
knee balancing system 10, comprising femoral member 12 and tibial
member 14 may be provided.
In the embodiment shown, femoral member 12 is adjustable to adjust
tension in the MCL, the LCL, or both. Adjustability may be achieved
by any suitable means, some of which are described in more detail
above and below. In one embodiment, for example, one or more
adjustment members 16, which may comprise screws, pins, levers,
spring-loaded mechanisms, shape memory materials or the like, are
coupled with femoral member 12 to provide adjustability. In some
embodiments, adjustment members 16 may be used for separately
adjusting femoral member 12 on either side to separately adjust
tension in the MCL or the LCL.
In general, femoral member 12, tibial member 14 and any of their
component parts may be manufactured from any suitable material now
known or hereafter discovered. For example, femoral member 12
and/or tibial member 14 in some embodiments may be manufactured
from one or more plastics, composites and/or metals, such as
aluminum, stainless steel, composite, cobalt-chrome, titanium, or
the like. These or any other suitable material(s) and combinations
of materials may be used in various embodiments.
As shown in FIG. 1A and subsequent figures, knee balancing system
10 is typically disposed primarily within the joint space of knee K
during a TKA surgery, thus providing for more convenient
manipulation of the knee, anatomical positioning of the patella
during surgery and the like. In alternative embodiments, however, a
knee balancing device or system could be engaged with the knee at a
location external to the knee joint. For example, in one embodiment
the device may comprise an externally applied frame that performs
the same functions as the devices described herein. In such
embodiments, some or all of the knee balancing device may be
located external to the knee joint, thus not fitting within the
knee joint space during the surgical procedure.
Referring now to FIG. 1B, the knee K is shown from a side view. In
this and subsequent figures, the collateral ligaments MCL and LCL,
other ligaments such as the posterior cruciate ligament PCL, and
the fibula Fi are removed for clarity. As is visible in this view,
femoral member 12 suitably comprises a stationary femoral member 18
an adjustable femoral member 17. Stationary femoral member 18 has a
base which is typically removably attached to a surface of the
distal femur F, often a cut surface at the distal end of the distal
femur F, and adjustable femoral member 17 is coupled with
stationary femoral member 18. Stationary femoral member 18 includes
at least one stationary posterior condylar member 18' disposed at a
substantially right angle relative to its base and extending
posteriorly therefrom to contact at least one of the medial and
lateral posterior condyles PC of the distal femur F. Typically,
stationary femoral member 18 includes two stationary posterior
condylar members 18', one for each posterior condyle PC. Similarly,
adjustable femoral member 17 has a base, the surface of which is
typically configured to contact the surface of tibial member 14
when the knee is in extension, and suitably includes one or more
(preferably two) adjustable posterior condylar members 17' disposed
at a substantially right angle relative to the base and extending
posteriorly therefrom to emulate the two posterior condyles PC. As
is described more fully below, posterior condylar members 17', 18'
allow femoral member 12 to be adjusted to balance ligament tension
in the knee K and also allow knee balancing system 10 to remain in
place within the joint space while the knee K is moved through a
range of motion. In various embodiments, stationary femoral member
18 and stationary posterior condylar members 18' may be either
multiple, couple parts or may be one piece or extrusion. Similarly,
adjustable fenioral member 17 and adjustable posterior condylar
members 17' are all one piece or extrusion in some embodiments, but
may alternative comprise multiple coupled parts.
Typically, adjustable femoral member 17 is movably engageable with
tibial member 14 to allow knee balancing system 10 to remain in
place within the knee joint space while the knee K is moved through
a range of motion. In some embodiments, such as the one shown in
FIG. 1 and subsequent figures, adjustable femoral member 17 and
tibial member 14 are movably engaged with one another via force
applied by the ligaments of the knee K, especially the MCL and LCL.
In other words, femoral member 12 and tibial member 14 are two
separate components which are brought together into a
movable/slidable coupling by ligament force. Such coupling of
adjustable femoral member 17 and tibial member 14 via ligament
force provides for dynamic balancing of the knee through a full
range of motion. In various alternative embodiments, ligament force
may not be used for coupling femoral member 12 with tibial member
14, and instead a passive mechanical coupling may be used.
With reference now to FIG. 1C, knee balancing system 10 is shown
with the knee K in flexion. It can be seen here that stationary
posterior condylar member 18' and adjustable posterior condylar
member 17' are slidably engageable with complementary grooves 20 on
tibial member 14. Thus, knee balancing system 10 is
movable/slidable through approximately a full range of motion of
the knee K, from full extension to full flexion and vice versa.
Referring to FIG. 1D, knee balancing system 10 is shown after an
adjustment has been made to adjustable femoral member 17. In one
embodiment, adjustable femoral member 17 is separately adjustable
on either side to separately adjust tension in the MCL and/or the
LCL. Such adjustment(s) may be achieved by any suitable means, such
as manual adjustment via a screw or other adjustment member,
self-adjustment via a spring-loaded mechanism, or the like. In the
embodiment shown, adjustment member 16 is adjusted to move
adjustable femoral member 17 relative to stationary femoral member
18. As adjustment member 16 is adjusted, adjustable femoral member
17 rotates relative to stationary femoral member 18, thus causing
adjustable posterior condylar member 17' to move away from
stationary posterior condylar member 18'. This movement creates a
larger joint space on the side of adjustment, thus tightening the
collateral ligament on that side. Meanwhile, the distal femoral
portion of adjustable femoral member 17 has rotated relative to the
distal femoral portion of stationary femoral member 18,
approximately about the long axis of the femur F. If adjustment
members 16 on both sides of adjustable femoral member 17 are
adjusted in the same direction, adjustable femoral member 17 may be
caused to move anteriorly or posteriorly relative to stationary
femoral member 18. Thus, adjustable femoral member 17 may be
adjusted rotationally as well as in an anterior/posterior
orientation.
With reference now to FIG. 1E, the knee K and knee balancing system
10 of FIG. 1D is shown in frontal view. Here it can be seen that
adjustment of adjustment member 16, on the lateral side of the
distal femur F, has caused adjustable posterior condylar member 17'
on the lateral side to move away from stationary posterior condylar
member 18' on the lateral side, thus increasing the height of the
joint space on the lateral side and rotating adjustable femoral
member 17 slightly, relative to the distal femur. Adjustable
femoral member 17 includes at least one positioning feature for
providing positional information for facilitation the TKA
procedure. As described above, the positioning feature(s) may
include any of a number of different features, such as apertures,
surface markers, embedded markers, fiducials, transmitters,
transponders, transceivers, sensors and/or the like. These
positioning features provide positional information that can then
be used to facilitate the TKA procedure. For example, apertures may
act as drill bit guides for drilling holes to apply a cutting guide
to the femur F to make subsequent bone cuts. In another embodiment,
apertures may contain fiducials or markers to provide information
to a navigational system and/or robotic surgical system for
positioning subsequent bone cuts or otherwise shaping the distal
femur F via milling, burring or the like. Various embodiments have
been fully described above, and any suitable positioning features
and positional information may be used in various embodiments.
In the embodiment shown, adjustable femoral member 17 includes two
apertures 24 as positioning features. Apertures 24 extend through
adjustable femoral member 17 and also through stationary femoral
member 18 such that apertures 24 may be used to guide a drill bit
to form holes in the distal femur F. Of course, as just discussed,
apertures 24 can serve any of a number of other functions, such as
carrying fiducials, sensors, markers or the like. In some
embodiments, corresponding apertures in stationary femoral member
18 are large enough to allow for movement of apertures 24 on
adjustable femoral member 17 such that apertures 24 extend all the
way to the cut surface of the distal femur F. When apertures 24 are
used to drill holes for a cutting guide, the balancing system 10 is
removed, holes are used to attach a cutting guide to the distal
femur F, and the cutting guide used to make subsequent bone cuts on
the femur F. Once these bone cuts are made, a femoral prosthetic
component is typically placed on the cut distal end of the femur.
These final bone cuts thus determine the position and orientation
of the femoral prosthetic component. Alternatively, positioning
information may be used to orient/position bone cuts by some other
means (not using a cutting guide), such by guiding a saw blade,
rotary cutter, bur or the like to make the actual bone cuts. In
some embodiments, position information may be used to guide a
robotic surgical system, to enhance the procedure via a
navigational system, or the like.
Also shown in FIG. 1E are two stationary femoral member attachment
screws 22. These screws are used to removably attach stationary
femoral member 18 to the distal femur F. Any other suitable
attachment device(s) may be used instead of or in addition to
attachment screws 22 to attach stationary femoral member 18 to the
distal femur F For example, adhesives, pins and/or the like may be
used in some embodiments.
FIGS. 2A-2C are anterior, posterior and side views, respectively,
of an embodiment of femoral member 12. These figures show two screw
holes 23 used for attaching stationary femoral member 18 to a
distal femur. They also show drill guide apertures 24 which are
formed by bushings 26 coupled with adjustable femoral member 17 and
stationary femoral member 18. Bushings 26 move along slots 27 in
stationary femoral member 17 as femoral member 12 is adjusted.
With reference now to FIGS. 3A and 3B, anterior and posterior
perspective views, respectively, of an embodiment of a knee
balancing system 100 are shown. Knee balancing system 100 suitably
includes a femoral member 140 and a tibial member 120. Femoral
member 140 may further include an adjustable femoral member 170
having adjustable posterior condylar members 170' and a stationary
femoral member 180 having stationary posterior condylar members
180'. In some embodiments, adjustable femoral member 170 and
adjustable posterior condylar member 170' will be one unitary piece
or extrusion, while in other embodiments they may be two or more
coupled pieces. Similarly, stationary femoral member 180 and
stationary posterior condylar member 180' may comprise a one-piece
construction or multiple pieces coupled together. In the embodiment
shown, stationary femoral member 180 comprises a distal femoral
plate coupled with two stationary posterior condylar members 180'.
Any suitable configuration, combination or manufacturing process
may be used in various embodiments.
Femoral member 140 may further include adjustment screw holes 161
for ingress/egress of adjustment screws (not shown), attachment
screws 220, drill guide apertures 240, bushings 260, slots 270
and/or any other features described previously above. Tibial member
120 may suitably include two grooves 200 or depressions to provide
for slidable coupling with femoral member 140. Generally, any of
the features described above may be applied to knee balancing
system 100.
Referring now to FIG. 3C, a knee balancing system 300 similar to
that described above is shown in frontal-perspective view. System
300 includes a tibial member 320 and a femoral member 340, the
femoral member 340 including an adjustable member 370 coupled with
a stationary member 380. Adjustable member 370 includes two
adjustable posterior condylar members 370', and stationary member
380 includes two stationary posterior condylar members 380'. In
FIG. 3C, one adjustment member 360a has been adjusted to move
adjustable posterior condylar portion 370' away from stationary
posterior condylar member 380' on that side, which would increase
the height of the joint space on that side if the device were in a
knee joint, and would also rotate adjustable femoral member 370
slightly relative to the distal femur. The pictured embodiment
includes two apertures 345 as positioning features, and disposed
within apertures 345 are two fiducials 390 (or markers, sensors or
the like) for providing positional information to a computer
navigation system or robotic surgery system. Such positional
information, for example, may include a dynamically balanced
orientation of the knee to make subsequent bone cuts on the femur
F.
With reference now to FIGS. 4A and 4B, the embodiment of knee
balancing system 100 from FIGS. 3A and 3B is shown in exploded view
to more clearly show its component parts. In this embodiment, the
component parts of knee balancing system 100 are the same as those
shown and described above in reference to FIGS. 3A and 3B. It can
be seen in FIGS. 4A and 4B that stationary femoral member 180 may
comprise three coupled parts--a stationary femoral member distal
plate 180 and two stationary posterior condylar members 180'. Such
parts may be coupled by any suitable means, such as pressure
fitting, sandwiching condylar members 180' between plate 180 and
adjustable femoral member 170, screws, adhesives, and/or the like.
Alternatively, stationary femoral member 180 may comprise one
unitary piece or extrusion.
An additional part shown in FIG. 4B is a bias spring 300. Bias
spring may be incorporated into femoral member 140 to allow for
rotation of adjustable femoral member 170 relative to stationary
femoral member 180. Alternative embodiments of knee balancing
system 100 may include any other suitable mechanism for allowing
such rotation, anterior-posterior adjustment, and/or any other
suitable adjustment(s).
In an exemplary method for enhancing a TKA procedure, a femoral
member is typically removably engaged with a distal femur of a
knee. Usually, the distal femur will have been cut to form a
surface for engaging the femoral member, but this is not required
in all embodiments. A tibial member is also engaged with a proximal
tibia of the knee, usually a cut horizontal surface of the tibia.
This tibial member may be provided as part of a dynamic knee
balancing system or may be an off-the-shelf tibial trial insert, in
various embodiments. In different embodiments, the tibial member
may be placed before the femoral member or vice versa. In one
embodiment, the femoral and tibial members are engaged with the
femur and tibia while the knee is in full or nearly full extension,
though in alternative embodiments they may be placed in flexion.
The height, thickness, or overall shape of the tibial member may
often be selected to provide a desired amount and balance of
ligament tension while the knee is in extension.
Generally, the knee is then moved from extension to flexion, and
the femoral member is adjusted to adjust tension in the MCL, LCL,
posterior cruciate ligament and/or other ligaments to achieve a
desired ligament balance in flexion. The knee may then be moved
through a range of motion, and one or more subsequent adjustments
may be made to the femoral member to adjust and balance ligament
tension through the range of motion. Most, if not all, such
adjustments and movements may, in some embodiments, be possible
while the patella of the knee remains in approximately its normal
anatomical position over the knee. This is advantageous because
patellar tracking, an important determinant of knee function, may
be assessed and adjusted during the TKA procedure. Typically, the
goal of the surgeon will be to achieve dynamic balancing of
ligament tension through the range of motion of the knee. Once this
balancing is achieved with the femoral and tibial members in place,
the positioning feature(s) on the adjustable femoral member provide
positional information to a surgeon, computer, robotic system
and/or the like, to help facilitate completion of the TKA
procedure. Using this positional information, subsequent cuts (or
drilling, burring or other shaping methods) are applied to the
femur, with such cuts/shaping determining how the femoral
prosthetic component of the artificial knee joint will be
positioned and oriented on the distal femur. The femoral prosthetic
component is then placed accordingly.
It is contemplated that any of the devices, systems and methods
described above may be incorporated with any suitable knee surgery
procedures or systems currently used or discovered in the future.
For example, inventive devices, systems and methods may be readily
incorporated with any number of different visualization, navigation
and/or robotic systems for performing a knee surgery, such as
image-guided systems for performing, planning or enhancing a TKA
procedure, robotic surgery systems such as the da Vinci.RTM.
Surgical System provided by Intuitive Surgical, Inc. (Sunnyvale,
Calif.), or the like. Any suitable imaging or visualization
modality and technique may be used with various embodiments of the
devices, systems and methods of the invention, such as but not
limited to infrared or ultrasound imaging.
Many suitable modifications and additions to the devices described
above may also be made without departing from the scope of the
invention. For example, in some embodiments a measurement device
may be included to measure ligament tension, and a display may
additionally be included to display an amount of measured ligament
tension to a user. In another embodiment, an amount of ligament
tension may be "dialed in" or otherwise entered into the device
such that the device will apply that amount of ligament tension
within the knee. Still other embodiments may include both tension
measurement and tension dial-in capabilities.
Therefore, while the foregoing is a complete and accurate
description of exemplary embodiments of the present invention,
various embodiments of the devices, systems and methods described
may include any number of modifications and additions. The
exemplary descriptions above should thus not be interpreted to
limit the scope of the invention as it is defined in the appended
claims.
* * * * *
References